This invention relates to reinforcing structures, particularly those of brick or masonry.
It is a known technique to reinforce such a structure by drilling into it, inserting a rigid bar or rod encased in a fabric sleeve, and injecting that sleeve with cementitious grout. The grout expands to fill the space around the rod, and some seeps through the fabric to bond to the drilling wall when set. Thus, the structure acquires rigid xe2x80x9cbonesxe2x80x9d.
However, it is not always desirable to have such rigidity. Sometimes, one wants reinforcement capable of xe2x80x9cgivingxe2x80x9d a bit without breaking, so largely maintaining its integrity and holding the structure together.
It is the aim of this invention to provide such a reinforcement with at least a limited sacrificial property.
According to the present invention there is provided a method of reinforcing a structure comprising:
drilling into the structure,
inserting into the drilling an elongated reinforcement core carrying over part of its length a permeable fabric sleeve, injecting cementitious grout into the sleeve to expand that against the wall of the drilling, some grout seeping through to bond to that wall and thereby locally securing said core, and
anchoring the reinforcing core at a zone distinct from the grouted sleeve to complete a reinforcing assembly.
This separation of the grouted sleeve and the anchoring zone reduces the rigidity of the reinforcement, which may distort in various ways whilst still holding the structure together even though it might be impaired.
In some versions the sleeve encases a tube which receives part of the core, there being an engagement between tube and core which progressively resists a pull on the core in the direction towards said anchoring zone.
In other words, the sleeved and grouted tube is rigid with the structure at one zone and the core is fixed to the structure at another zone (the anchoring zone). If the zones start to separate, the core meets resistance within the tube that progressively increases. Small movements within the structure are therefore easily accommodated, but should those movements increase, the reinforcement acts ever more strongly to stop them.
This progressive resistance may be provided by the tube having a gradual internal taper, narrowing in said direction, and by the core having a plug with an easy fit in the larger end of the tube, movement of the core in said direction causing the plug to wedge into the tube. Alternatively, the tube could be a cylinder, the core a piston fitting the cylinder, and the resistance a liquid against which the piston acts in said direction, there being a highly restricted route for the liquid to escape from its space within the cylinder. In another arrangement the progressive resistance may be provided by a resilient element, such as a helical spring or a thick rubber sleeve, surrounding the core and acting between a formation on the core and an abutment internal of the tube.
The anchoring can be provided within the drilling by another, similar grouted sleeve and tube assembly, within which another part of the core engages with progressive resistance to its movement in the reverse direction.
Alternatively, the anchoring may be provided within the drilling by another grout filled fabric sleeve encasing another part of the length of the core directly so that the grout bonds to the core and through the fabric to the drilling wall.
The anchoring can be external of the drilling, the core projecting clear of the structure and being held by an abutment against the surface around the mouth of the drilling. Typically, this might be achieved by screw-threading the projecting end of the core to receive an apertured plate clamped against the structure by a nut.
In all these versions the core may have at least one further permeable fabric sleeve between the first mentioned sleeve and the anchoring zone, and cementitious grout will be injected into the or each further sleeve to bond that to the drilling wall. There would thus be a xe2x80x9cchainxe2x80x9d of reinforcements along the drilling. Should there be any move movement within the structure, the individual sections will stay rigid, but each can move relative to the next one.
The or each further grout filled fabric sleeve can encase the core directly so that the grout bonds to the core or it can encase a tube through which the core freely passes.
To keep the sleeves apart during insertion in the drilling and thus ensure that there are exposed portions of core between each pair of adjacent sleeves, spacers may be provided, each spacer being weak in relation to the solidified grout reinforcements to either side.
With several sleeves to fill, conveniently a conduit leads from the mouth of the drilling through one or more sleeves to a remote sleeve for the injection of grout, the remote sleeve being filled first, the conduit then being partially withdrawn to terminate in the next sleeve, that sleeve being filled next via the same conduit, and so on until the sleeve adjacent the mouth is filled and the conduit is wholly withdrawn.
When the anchoring zone and the or each grouted sleeve are separated longitudinally of the drilling, the core will be locally exposed and therefore be susceptible to being bent at the or each exposed portion by distortion of the surrounding structure. But it may be beneficial to have a preferential mode of bending, in which case the core could be a plurality of parallel reinforcing rods bundled in a manner such that their collective ability to bend is easier in some directions than others.
It may also be useful for each sleeved and grouted section or group of consecutive sections to have its own core joined to another core in a gap between sections. The joint can give certain characteristics. For example, adjacent cores can be different, one being stronger than the other, and so the weak one will bend first, particularly if a fixed joint is made between adjacent cores. But there could be a flexible or linked joint, and a linked one could be loose enough also to allow limited longitudinal expansion of the reinforcing assembly.
In all these arrangements a relatively weak joint, compared with others along the assembly, can be provided so that, if there is to be failure of the structure it will tend to be around that joint.
Instead of one or more reinforcing rods the core may be at least one wire. Particularly if multi-strand and laid with a twist, it will have an inherent stretchability, and so may be firmly secured to the structure at both ends and put under moderate tension and yet allow lengthening of the reinforcements without any extra measures being taken. A wire will of course allow bending or transverse displacement of the reinforcement. But to increase the scope for extension the wire may be kinked between sections.